Heavy Duty Trucking

SEP 2014

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44 HDT • SEPTEMBER 2014 www.truckinginfo.com
the 1930s. Like them, an Achates OP
has no intake or exhaust valves, and
no heavy cylinder heads.
The relatively simple OP design
promises a substantial increase in fuel
economy — about 30% better than
current conventional piston engines,
say Achates executives and engineers.
Moreover, they say their OP diesels
will meet current and future emis-
sions limits and cost 10% less to
manufacture. In contrast, a govern-
ment-sponsored study concluded that
a 23% fuel economy improvement
would cost the buyer of a traditional
engine about $23,000, says David
Johnson, Achates' president and chief
executive officer.
Such financial advantages have the
attention of commercial interests,
including Fairbanks Morse Engine, a
long-time builder of opposed-piston
diesels for transportation, industrial,
marine and military use. FM, which
sells diesel and dual-fuel OP engines,
wants the refinement that Achates
people are applying to the 80-year-old
concept.
No, the opposed-piston concept
is not new. The 30% fuel-savings
figure was established in the mid
1930s by Junkers of Germany in its
Juno 205 OP aircraft engine, Johnson
explained.
Achates, co-founded by an aircraft
designer and an engineer, began mod-
ernizing the OP concept in 2004.
It has assembled a team of highly
trained and experienced engineers
performing intricate design work.
They've got engines running on test
stands, and are working slowly and
deliberately to be sure they're getting
every advancement right.
For example, engineers are design-
ing a wrist pin bearing with a contour
that reduces friction while still
standing up to constant pounding as
it transfers power toward the crank-
shafts. Conventional piston engines
have those parts, but how they work
in OP engines is subtly different,
Johnson said. Of course modern OP
diesels have electronic controls. And
to further meet emissions limits, an
energy compared to conventional
engines with their single piston and
combustion chamber per cylinder.
Brake-thermal efficiency of a 4.9-li-
ter, three-cylinder/six-piston Achates
OP diesel now being tested is 47.8%,
compared to typical BTEs in the high
30- to low 40% range for convention-
al midrange diesels. The best current
15-liter truck engine is the Cummins
ISX, with 43.4% BTE, Johnson said.
But Achates is projecting 51.5% BTE
for an engine of comparable power.
(A 50% BTE is one of the goals of
the U.S. Department of Energy's
SuperTruck program, and so far only
one of the research teams developing
demo trucks has surpassed that.)
In addition, an OP diesel can burn
many fuels, and will readily handle
natural gas with just a 1% shot of
diesel as the ignition agent.
An Achates heavy truck engine of
11 to 13 liters in displacement will
produce 400 to 600 horsepower and
1,475 to 1,625 pound-feet, Johnson
OP diesel uses exhaust-gas recircu-
lation and exhaust aftertreatment
devices, but needs less equipment.
One principle responsible for an
OP engine's high efficiency is its large
amount of piston travel versus bore
size, a ratio of 2.4 to 1, explained
Johnson and James Lemke, Ach-
ates' co-founder and chief scientist.
Another is the central combustion
chamber, which works comparatively
slowly and gets multi-metered fuel
from two injectors. These reduce
heat rejection and use more of a fuel's
FuelSmarts
The best current
15-liter truck engine
is the Cummins ISX,
with 43.4% brake-
thermal efficiency,
but Achates is
projecting 51.5% BTE
for an OP engine of
comparable power.
said. An extra port in each cylinder
will enable engine braking at similar
levels. A heavy-duty engine will have
three cylinders and six pistons, but
with a larger bore and stroke than
that 4.9-liter light-truck engine's.
The smaller engine, being tested
on a dynamometer stand for the
military, has horizontal cylinders with
accessories cantilevered at various
points. But an OP can be configured
and packaged to fit the vehicle it's
intended for. For trucks, the cylinders
are likely to be vertical or slanted.
Without cylinder heads, it'll sit low in
the chassis, allowing a low hood and
nose to reduce air drag and improve
driver visibility. With reduced heat re-
jection, the radiator can be relatively
small and fit in that small nose.
The Achates team expects to
have engines running in trucks in
about three years, Johnson said.
In five years they'll probably be in
production. Achates, though, won't
build them; instead it will license its
patented technology for combustion,
piston design, cylinder cooling and
air handling to established engine
companies who can use existing
facilities to produce them. "We're
in touch with just about everybody
in the world" who makes engines,
Johnson said. n
Trucks as
elecTric Trolleys
A
project testing overhead lines to
power trucks with electricity is
moving forward along selected high-
way lanes near the ports of Los Ange-
les and Long Beach in California.
The South Coast Air Quality Man-
agement District, which is the air
pollution control agency for LA and
surrounding areas, is working with
Siemens and Mack to demonstrate
a catenary system — overhead
electrical lines that supply trucks
with electric power, similar to how
trolleys or streetcars are powered on
city streets.
Siemens and the Volvo Group,
through its Mack Trucks, are devel-
oping a demonstration vehicle for